Thanks for the suggestions!
It's strange that you observe that with the flamethrower, because the damage the fireballs do falls off linearly with distance - perhaps it's because the fire spreads out further, and anything that isn't destroyed is pushed back at about the same rate? We could look at making the push-back rate taper off as well, if we don't already.
Regarding forcing the player view to the ship in VR - forcibly moving the camera around in virtual reality is generally recognised to be a major faux pas these days; it can lead to major instant nausea, so we leave the camera completely free at all times in VR mode. Perhaps we could add an option for those who really don't mind the nausea to enable it if they want it, with a suitable warning.
Outside of VR mode, you can enable camera locking to ship temporarily to re-orient yourself and then free the camera again if you want to by pressing X.
When you exit a portal in a sphere containing rocks and enemies, any enemies that fly into the open portal are destroyed and any rock it happens to overlap is carved out as a neat circle already. However, if you exit the portal quickly it's still possible to collide with the remains; I guess this is a look-before-you-leap scenario! Likewise, you can use portal opening as a weapon, by timing your hyperjump carefully so you destroy some enemies on the other side.